In folding apparatuses, useable, in particular, for products of a rotary printing press, product sections or products are further processed in several successive and partially alternatively selectable processing stages. The alternative assignment of each of the product sections or products to one or another of several processing stages takes place by the use of a product shunt. In generally conventional folding apparatuses, the product shunt, as well as the tools or apparatus of the subsequent processing stages, are typically driven via gears from a main drive mechanism of the folding apparatus or its transport devices and are synchronized with them. However, if the product sections or products, prior to their entry into the shunt and/or prior to their entry in the downstream located processing stage, are not always exactly oriented, damage to the products can occur. This may result in a reduction in quality of the resultant product and may even result in the stoppage of the installation, either in the course of the passage of the product sections through the shunt, or during subsequent further processing of the product sections.
A product shunt of a folding apparatus, with two downstream located longitudinal folding apparatuses, is disclosed in DE 198 02 995 C2. A sensor, for use in detecting the phase relation of the product, is located upstream of the product shunt. Another sensor is located downstream of each of the two succeeding longitudinal folding apparatuses and is usable for detecting jams in these apparatuses. The three sensors, another sensor, which is usable for detecting the number of revolutions of the main drive mechanism, as well as a switching device for setting a production type, are all connected with a regulating arrangement for controlling the product shunt. The regulating arrangement acts on a step motor which is connected with the shaft of the product shunt.
A longitudinal folding apparatus is known from DE 40 20 937 C2. A folding blade can be moved toward and away from the folding apparatus by the use of a cam disk.
DE 199 43 165 A1 discloses a folding blade of a longitudinal folding apparatus. The folding blade can be moved into and out of the folding apparatus by the use of coils which generate electromagnetic force.
Longitudinal folding apparatuses are generally known and are employed in the printing industry, primarily in the finishing of printed products. The printed products are pushed into the folding gap by the folding blade and are longitudinally folded in it. The entry direction of the printed products into the longitudinal folding apparatus extends transversely with respect to their subsequent movement through the folding gap. It is therefore necessary to slow the printed products down, prior to their passage through the folding gap. Braking brushes, which gradually slow down the incoming printed products by friction, as well as stationary buffers, against which the printed products bump, and which printed products are abruptly braked by this, are known for this purpose in generally known longitudinal folding apparatuses. To avoid damage to the printed products at the buffers, it is necessary to reduce the speed to a low value. However, this value may in no case be zero. If the speed becomes zero, the printed products do not reach the buffer, and a jam occurs. The extent of the slow-down, by the use of the brushes, is determined by the friction that they exert on the printed products, and ultimately by the position of the latter. If it is intended to fold printed products of varied thickness, while the position of the brushes remains the same, the friction, which is exerted by the brushes, greatly increases with the thickness of the products. A thick product may possibly get stuck between the brushes and thus will not reach the buffer, while a thin product will bump against the buffer with such great speed that it becomes damaged in the process. Therefore, the position of the brushes must be matched to the thickness of the printed products.
The friction between printed products and brushes is also a function of the surface condition of the printed products. Products made of smooth paper can bump against the buffer too rapidly, while products made of rough paper, even though being of the same thickness and the same weight as the smooth paper products, possibly do not reach the buffer.
A further problem arises from the fact that the amount of kinetic energy of the printed products, which is dissipated at the brushes, is a result of the product of brush friction and the length of the braking path. The kinetic energy dissipation is independent of the entry speed of the printed products into the brushes. Changes of this entry speed, regardless of whether these changes are intentional or unintentional, therefore have a very strong effect on the bumping speed of the printed products on the buffer.
For all practical purposes, it is necessary to adjust the position of the brushes for each printing job in order to assure the correct functioning of the longitudinal folding apparatus. Based on the multitude of influencing parameters which are involved, the adjustment of the brush position can often only take place empirically, which trial and error adjustment results in a large outlay of time and costs.
A further basic problem, which occurs in connection with high entry speeds of the printed products, even when they are braked to such an extent that damage, because of bumping against the buffer, does not occur, results from the fact that the printed products change their position and orientation in the course of the braking process. In many cases, following its braking, a printed product assumes a twisted position in the longitudinal folding apparatus, in which twisted position, the front edge of the printed product no longer extends perpendicular to the folding gap. The printed product is therefore not folded, in the desired way, in the center in the course of subsequent folding, during which subsequent folding the printed product is pushed, in its twisted position, into the folding gap by the folding blade, and now has an oblique fold.
Premature folding can also occur if printed products are delayed in their entry the longitudinal folding apparatus. This is true particularly if driving of the folding blade, which is the tool of the processing change is provided by a main drive mechanism.
EP 1 211 212 A2 shows a folding blade control device of a longitudinal folding apparatus with a sensor arranged upstream of the longitudinal folding apparatus. A control of a folding blade triggering time is determined as a function of the speed of the transported product sections, as determined by the sensor.
DE 198 28 625 A1 relates to a transverse folding device for the transverse folding of sheets. It includes a folding blade that is inclined in the transport direction, as well as an automatic control for the position or the correct separation of the sheets. The device is capable of transversely folding sheets of paper once or several times.